#include<iostream>
using namespace std;
int main(){
	int n,m,x,y;
	cin>>n>>m>>x>>y;
	int a[n+1][m+1];
	for(int i=0;i<=n;i++){
		for(int j=0;j<=m;j++){
			a[i][j]=1;
		}
	}
	a[x][y]=0;
	if(x==0 && y==0){
		a[x+2][y+1]=0;
		a[x+1][y+2]=0;
	}
	else if(x==0){
		a[x+2][y-1]=0;
		a[x+1][y-2]=0;
		a[x+2][y+1]=0;
		a[x+1][y+2]=0;
	}
	else if(y==0){
		a[x-2][y+1]=0;
		a[x-1][y+2]=0;
		a[x+2][y+1]=0;
		a[x+1][y+2]=0;
	}
	else if(x==1 && y==1){
		a[x-1][y+2]=0;
		a[x+2][y-1]=0;
		a[x+2][y+1]=0;
		a[x+1][y+2]=0;
	}
	else if(x==1){
		a[x-1][y-2]=0;
		a[x-1][y+2]=0;
		a[x+2][y-1]=0;
		a[x+1][y-2]=0;
		a[x+2][y+1]=0;
		a[x+1][y+2]=0;
	}
	else if(y==1){
		a[x-2][y-1]=0;
		a[x-2][y+1]=0;
		a[x-1][y+2]=0;
		a[x+2][y-1]=0;
		a[x+2][y+1]=0;
		a[x+1][y+2]=0;
	}
	else{
		a[x-2][y-1]=0;
		a[x-1][y-2]=0;
		a[x-2][y+1]=0;
		a[x-1][y+2]=0;
		a[x+2][y-1]=0;
		a[x+1][y-2]=0;
		a[x+2][y+1]=0;
		a[x+1][y+2]=0;
	}	
	for(int j=0;j<=m;j++){
		if(a[0][j]==0){
			for(int i=j;i<=m;i++){
				a[0][i]=0;
			}
			break;
		}
	}
	for(int j=0;j<=n;j++){
		if(a[j][0]==0){
			for(int i=j;i<=n;i++){
				a[i][0]=0;
			}
			break;
		}
	}
	for(int i=1;i<=n;i++){
		for(int j=1;j<=m;j++){
			if(a[i][j]==0){
				continue;
			}
			else{
				a[i][j]=a[i-1][j]+a[i][j-1];
			}
		}
	} 
	cout<<a[n][m];
}
